Method and means for minimizing fire in dynamo-electric machinery



July 30, 1929. J. F. JOHNSON 1,722,632

METHOD AND MEANS FOR MINIMIZING FIRE IN DYNAMO ELECTRIC MACHINERY Original Filed July 16, 1923 J EJo/maoh INVENTOR ATTORNEY Patented July 30, 1929.

UNITED STATES PATENT OFFICE.

JOSIAH F. JOHNSON, OF SWARTHMORE, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENN SYL- VANIA.

METHOD AND MEANS FOR MINIMIZING FIRE 1N DYNAMO-ELECTRIC MACHINERY.

Application filed July 16, 1923, Serial No. 651,781.

My invention relates to a method of and apparatus for preventing the initiation and maintenance of fires in dynamo-electric machinery and it has for its object to provide a system of the character designated which shall be simple and inexpensive in construction and operation and highly effective in producing the result set forth.

In the accompanying drawing, Fig. 1 is a side view, partiall in section and partially in elevation, of a ynamo-electric machine, together with a closed ventilating system therefor, embodying one form of my invention, and Figs. 2, 3 and 4 are fragmentary views illustrating modifications of the structure shown in Fig. 1.

In the operation of dynamo-electric machines and in particular of large turbo-alternators, the problem of fire is extremely serious, inasmuch as the vast quantities of air blown through machines of this type tend to cause extremely violent combustion when a fire starts by reason of a short circuit or some other cause and total or partial destruction of the insulating material on the windings quickly follows, resulting in serious expense and delay to restore the gener ator to serviceable condition. Such combustion can take place only to such extent as oxygen is available to support it. It has been proposed to cool and ventilate dynamo-electric machines of the character above designated by means of a closed ventilating sys tem, in order to limit the quantity of oxygen available to support combustion; also in order to minimize the amount of dust and dirt present in the atmosphere which collects in the windings and impairs the effectiveness of the cooling. It has further been proposed to inject large amounts of flamesmothering gas, such as carbon dioxide, into closed ventilating systems of the above character upon the incidence of fire. Inasmuch as it is commercially impracticable to maintain such a so-called closed system tight against leakage, any flame-smothering gas admitted will gradually become dissipated and diluted with atmospheric air.

In accordance with the present invention, I provide a dynamo-electric machine with a closed ventilating system, including a gas cooling device, and I further provide means for removing or fixing some or all of the free oxygen content of the air within the Renewed January 17, 1929.

ventilating system, thus rendering the resultant medium incapable of maintaining combustion and minimizing the danger of the spread of fire in the winding of the machines. I may fix the free oxygen in the form of a gas, such as carbon dioxide, by maintaining a flame or a body of decomposing animal or vegetable matter in the ventilating system, or I may fix the oxygen in solid form, as by maintaining incandescent iron filings within the system.

Referring now to the drawing for a more detailed understanding of my invention, I show a turbo-alternator at 5 in Fig. 1, the machine comprising the usual frame 6 carrying an armature 7 and surrounding a field member 8, the ends of the machine being tightly closed as by end bells 9 and 10.

A duct 11 leads from the bottom of the end bell 10 by a de-oxidizing device 12 constructed in accordance with my invention; thence through a cooling device 13 and back to the bottom of the end bell 9 so that free circulation of the cooling medium may take place through the elements designated. I have indicated only the most rudimentary system of ventilating within the dynamoelectric machine itself, in that I have shown the cooling medium as passing only through the air gap, but it will be well understood to those versed in the art that any suitable cooling and ventilating system may be applied to the machine itself without departing from the spirit of my invention.

The flow of cooling medium through the closed ventilating system thus far described is established and maintained as by vanes let mounted on the end of the rotor 8. Referring specifically to the de-oxidizing device 12, I show a blow-pipe 13 provided with fuel from a supply line 25 through a valve 15, this fuel being either liquid or gas, as may be preferred. Air for assisting in the maintenance of combustion may be supplied from an air pressure line 16 through a valve 17.

An oxygen detecting element 18 may be placed within the system 11 and may take the form of certain phosphorus compounds which rapidly develop heat when exposed to oxygen in excess of a predetermined percentage amount, these phosphorus compounds being associated with a resistance wire which is inserted in one side of a Wheatstone bridge 19, unbalancing of this bridge operating a solenoid 20 to affect the degree of the opening of the valves 15 and 17.

A fuel by-pass 21 may be inserted around the valve 15 and be subject to control, as by a valve 22.

A peep-hole 23 is provided for observing the size and character of the flame 24. It will be understood that the flame 2 1 may be shielded in any desired manner so as to prevent its being extinguished by the rapid flow of gas through the system, but the particular type of shielding system forms no part of the present invention, and the showing thereof is therefore omitted in'the interests of simplicity and clarity.

Having thus described the arrangement 1 of the system of Fig. 1, the operation thereof is as follows:

" When first installed, the ventilating system 11 is, of course, filled with ordinary air and upon starting'upthe machine, this air is circulated as by the vanes 14, absorbing heat within the machine 5 and giving up said heat within the device 13, whence it i may be returned, for example, to the boiler feed. The flame 24 may then be started as by opening the valve 22 and permitting the fuel to pass into the ventilating system, no

' air being supplied from outside the system,

so that all the oxygen for the support of the flame 24: is taken from within the system, the. free oxygen rapidly being converted into carbon dioxide or, in extreme cases, into carbon monoxide. Such small amount of heat as is imparted to the ventilating medium by the flame 24: is largely removed by the passage of the medium through the tie vice 13 so that the machine 5 is not heated thereby to any appreciable extent.

It will be obvious that after the burning of the flame 2 1 for a predetermined time,

the free oxygen will have been taken up to such an extent that the flame may become sooty and eventually go out, leaving the system to gradually acquire a free oxygen content by the infiltration of fresh air, and it is accordingly desirable to maintain a flame and to ensure the continuous supply of products of combustion to the interior of the space. To this end, the air pressure may be admitted through the conduit 16 and the flame 24' thereafter partially maintained thereby so that the flame exists in spite of the deficiency of free oxygen withinthe ven- T tilating system. By supplying the air under pressure, the pressure within the entire ventilating system may be maintained slightly above atmospheric, resulting in outward leakage at all points and effectively preventing the infiltration of fresh air.

If desired, the control of the valves 15 and 17 may be entirely manual, but with the automatic control device illustrated at 181920, the operator need give little or no attention to this action,ran increase in the percentage oxygen content within the ventilating system above a predetermined point resulting in the rapid evolution of heat in the element 18, unbalancing the bridge 19 and energizing the solenoid 20 to open the valves 15 and 17, thus increasing the flame 24 and rapidly diminishing the oxygen content. Vhen the oxygen content falls below a predetermined value, the element 118 rapidly cools off, again balancing the bridge and releasing'the solenoid 20, permitting the valves 15 and 17 to return to a position of minimum opening just sufficient to maintain a stable flame at the point 24.

It will be, of course, understood that when operating with the automatic valves 15 and 17 the by-pass valve 22 is substantially closed.

Referring to the simpler form of device shown in Fig'2, the duct 11 is shown provided with an opening in the side thereof at 30, a small shelf 31 being mounted within said opening, a lamp 32 may be slid in upon said shelf when desired, and the condition of the flame may be noted as through the peep-hole 33.

Referring to the form' of my invention shown in Fig. 3. the duct 11" through which the cooling medium passes is shown as provided with a mass of oxygen-absorbing material at 35, such for example as iron filings or copper filings. A heating element as of the electric type is shown at 36, by which the mass 35 may be-brought to such a temperature as to readily combine with oxygen, and it will be obvious from the foregoing discussion that by supplying current to the heating device 36, the oxygen content of the entire ventilating system may be quickly and effectively reduced.

Referring to the form of my invention shown in Fig. 4, a conduit 11 is shown as provided with a receptacle 10 containing any suitable decomposing animal or vegetable material, the affinity of such substances for free oxygen being well-known and the action of the contents of the receptacle 10 is to, at all times, operate to reduce the oxygen content of theventilating system to a low value.

While I have shown my invention inseveral forms, it will be obvious to those skilled in the art that it is not so limited, but is sus-' ceptible of various other changes and modifications without departin from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is:

l. The combination with a dynamo-electric machine, of means forproviding a closed circulation of gaseous cooling medium there through, and means for automatically re- "and means therefor, and means for maintaining an atmosphere therein composed essentially of the ingredients of air in which the oxygen has been replaced by oxygen compounds.

4. The combination with a dynamo-electric machine, of a closed ventilating system therefor including a cooling device, means for maintaining an atmosphere of the ingredients of air devoid of free oxygen in said system, and means for continuously circulating said atmosphere through said dynamo-electric machine and said cooling device.

5. The combination with a dynamo-electric machine, of a closed ventilating system therefor which isinitially filled with air, and means for chemically absorbing the oxygen from said air and from air subsequently entering said system.

6. The combination with a dynamo-elec tric machine, of a closed ventilating system therefor including a gas-cooling device, said system being initially filled with air, and chemical means for absorbing the oxygen from said air and from air subsequently entering said system.

7. The combination with a dynamo-electric machine, of a closed ventilating system therefor which is initially charged with air, means for chemically combining with the free oxygen in said air, and means for automatically increasing the activity of said combining means when the free oxygen content of said medium exceeds a predetermined amount.

8. The combination with a dynamo-electric machine, of a closed ventilating system therefor which is initially charged with air, means for chemically combining with the free oxygen in said air, a cooling device in said system through which the medium within said system is continuously passed, and means for automatically increasing the activity of said combining means when the free oxygen content of said medium exceeds a predetermined amount.

9. The combination with a dynamo-electric machine provided with a closed ventilating system, of means for maintaining a flame within said system for fixing the free oxygen content of the air within said system, and means for supporting said flame with air at a pressure slightly above atn1ospheric, whereby said flame may be maintained in the presence of an inadequate oxygen supply within said system and whereby the infiltration of fresh air to said system is minimized.

10. The combination with a dynamo-electric machine provided with a closed ventilating system, including a gas-cooling device, of means for maintaining a flame within said system for fixing the free oxygen content of the air within said system, and means for supporting said flame with air at a pressure slightly above atmospheric, whereby said flame may be maintained in the presence of 'an inadequate oxygen supply within said system and whereby the infiltration of fresh air to said system is minimized.

11. The combination with an electrical apparatus having a closed ventilating system for cooling the same, a cooling gas being inclosed in an enclosure and means being provided for circulating said cooling gas through said electrical apparatus within said enclosure, of means within said enclosure for chemically removing or fixing some or all of the free oxygen content of said cooling gas.

12. The combination with a dynamo-elec tric machine having a closed ventilating system for cooling the same, a cooling gas being inclosed in an enclosure and means being provided for circulating said cooling gas through said dynamo-electric machine within said enclosure, of a de-oxidizing agent within said enclosure.

13. The combination with an electrical ap paratus having a closed ventilating system for cooling the same, a cooling gas being inclosed in an enclosure and means being provided for circulating said cooling gas through said electrical apparatus within said enclosure, of a controllable de-oxidizing agent within said enclosure, and chemically operative detective means responsive to an excessive proportion of free oxygen within said enclosure for giving an indication thereof.

I l. The combination with an electrical apparatus having a closed ventilating system for cooling the same, a cooling gas being inclosed in an enclosure and means being provided for circulating said cooling gas through said electrical apparatus within said enclosure, of tie-oxidizing means within said enclosure for chemically removing or fixing some or all of the free oxygen content of said cooling gas, detecting means responsive to an excessive proportion of free oxygen within said enclosure, and means responsive to said detecting means for automatically increasing the activity of said (lo-oxidizing means.

15. The combination with an electrical apparatus having a closed ventilating system for cooling the same, a normally substantially inert cooling gas being inclosed in an enclosure and means being provided for circulating said cooling gas through said electrical apparatus Within said enclosure, of chemically operative detecting means responsive to an excessive proportion of free oxygen within said enclosure.

16. The combination with an electric ma chine, of a closed cooling system therefor which is initially filled with air, and means for chemically absorbing the oxygen from said air and from air subsequently entering said system.

17. The combination with an electrical machine, of a closed ventilating system therefor including a cooling device, said system being initially filled with air, and chemical 'means for absorbing the oxygen from said air and from air subsequently entering said system.

18. The combination with an electric machine, of a closed cooling system therefor which is initially charged with air, means for chemically combining with the free oxygen in the air, and means for automatically increasing the activity of said combining means when the free-oxygen content of said medium exceeds a predetermined amount.

19. The method of maintaining an inert atmosphere in a casing containing an electrical apparatus which consists in burning fuel and passing the products of combustion into the casing.

20. The method of maintaining an inert atmosphere in a casing containing an electrical apparatus which consists in burning fuel and circulating the products of combustion through the casing.

In testimony whereof, I have hereunto subscribed my name this 3rd day of July, 1923.

JOSIAH F. JOHNSON. 

